U.S. national parks have never been more popular than they are right now -- and some are requiring reservations just to get in.

(CNN) - Ads are coming to Instagram's popular Explore page, one of the last ad-free places on the photo-sharing network. On Wednesday, the Facebook-owned company said it will start placing ads on that section of the app in the coming weeks. The Explore page recommends posts it predicts a user would like based on other posts they've looked at in the past. Susan Buckner Rose, Instagram's director of business product marketing, said it felt like the right time to bring ads to Explore. Instagram recently announced branded content ads, which allow brands to make social media influencers' sponsored content posts appear as ads so a bigger audience sees them.